Articulated stapling with fire lock

ABSTRACT

A loading unit for a surgical apparatus includes a shaft assembly, an end effector extending from the shaft assembly, an articulation rod, and a fire lock assembly. The articulation rod positioned to articulate the end effector relative to the shaft assembly between an unarticulated position and an articulated position. The fire lock assembly movable in response to movement of the articulation rod. The fire lock assembly configured to selectively prevent the end effector from firing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/014,000, filed Jun. 21, 2018, the entire contents of which are incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to surgical stapling apparatus, devices and/or systems for performing endoscopic surgical procedures and methods of use thereof.

BACKGROUND

Surgical stapling apparatus that clamp, cut and/or staple tissue between opposing jaw structure are well known in the art. Such surgical stapling apparatus can include loading units with an end effector having two elongated jaw members used to capture or clamp tissue. One of the two jaw members usually carries a staple cartridge that houses a plurality of staples while the other of the two jaw members has an anvil for forming the staples as the staples are driven from the staple cartridge. Generally, a stapling operation is effectuated by a cam bar, a drive sled or other similar mechanism having a cam member that travels longitudinally through channels defined in the staple cartridge and acts upon staple pushers in the channels to sequentially eject the staples from the staple cartridge. Since these stapling apparatus are typically utilized during endoscopic or laparoscopic procedures in which surgery is performed through small incisions or narrow cannulas inserted through the small incisions, such stapling operation is often effectuated when the end effector is disposed in an articulated position relative to the stapling apparatus to enable the end effector to reach remote surgical sites within a patient's body.

SUMMARY

Accordingly, the present disclosure is directed to a surgical stapling apparatus for use during laparoscopic and/or endoscopic surgical procedures that can be employed to provide firings of the surgical stapling apparatus while an end effector thereof is disposed in an articulated position. The surgical stapling apparatus includes a fire lock assembly to prevent the surgical stapling apparatus from firing when the end effector is not in the articulated position. Advantageously, the fire lock assembly prevents inadvertent firing of the surgical stapling apparatus when the end effector is unarticulated (or not articulated to a predetermined angle such as about 90 degrees), but enables clamping and/or unclamping of anvil and cartridge assemblies of the end effector for advancing end effector through small diameters such as through a cannula of a surgical access device.

In one aspect of the present disclosure, a loading unit for a surgical apparatus is provided. The loading unit includes a shaft assembly, an end effector coupled to the shaft assembly, an I-beam assembly supported in the shaft assembly, and a fire lock assembly supported on the shaft assembly. The end effector is positioned to articulate relative to the shaft assembly between an unarticulated position and an articulated position. The I-beam assembly is selectively movable relative to the end effector to fire the end effector. The fire lock assembly is configured to prevent the I-beam assembly from firing the end effector when the end effector is disposed in the unarticulated position.

In some embodiments, the I-beam assembly may include one or more knife bars that support an I-beam configured to advance through the end effector to fire the end effector. The fire lock assembly may include a fire lock that is positioned to engage the one or more knife bars to prevent the I-beam from firing the end effector when the end effector is in the unarticulated position. The fire lock and the one or more knife bars may be disengaged when the end effector is in the articulated position such that the I-beam can advance through the end effector for firing the end effector.

In embodiments, the end effector may include an anvil assembly and a cartridge assembly that are pivotally coupled together and movable between an unclamped position and a clamped position.

In certain embodiments, the I-beam assembly may be configured to position the anvil and cartridge assemblies in the clamped position when the end effector is disposed in the unarticulated position or the articulated position.

In some embodiments, the fire lock assembly may include a fire lock and a spring that is positioned to urge the fire lock toward a first position. The fire lock may be positioned to prevent the I-beam assembly from advancing through the end effector when in the first position.

The loading unit may further include an articulation rod that is movable to articulate the end effector relative to the shaft assembly. The articulation rod may be positioned to move the fire lock to a second position as the end effector moves from the unarticulated position to the articulated position. The I-beam assembly may be positioned to advance through the end effector to fire the end effector when the fire lock is disposed in the second position.

In certain embodiments, the loading unit may further include a pivot guide that may be positioned to curve the I-beam assembly into the end effector.

According to another aspect of the present disclosure, a surgical stapling apparatus is provided. The surgical stapling apparatus includes a shaft assembly, an end effector coupled to the shaft assembly, a knife bar, and a fire lock. The end effector is coupled to the shaft assembly and positioned to articulate relative to the shaft assembly between an unarticulated position and an articulated position. The knife bar supports an I-beam and is selectively movable relative to the shaft assembly. The fire lock is configured to engage the knife bar to prevent the I-beam from advancing through the end effector when the end effector is disposed in the unarticulated position.

In some embodiments, the end effector may include an anvil assembly and a cartridge assembly that are movable between an unclamped position and a clamped position. The I-beam may be positioned to advance into a proximal end portion of the end effector to move the anvil and cartridge assemblies from the unclamped position to the clamped position. The fire lock may disengage from the knife bar as the end effector moves from the unarticulated position to the articulated position. The fire lock may prevent the I-beam from advancing distally beyond the proximal end portion of the end effector when the end effector is disposed in the unarticulated position.

In some embodiments, the end effector may be articulated approximately 90 degrees relative to a longitudinal axis defined through shaft assembly when the end effector is disposed in the articulated position.

The surgical stapling apparatus may further include an articulation rod supported by the shaft assembly. The articulation rod may be configured to articulate the end effector relative to the shaft assembly. The articulation rod may define an elongated slot therethrough that may be positioned to receive the fire lock therein. The fire lock may be positioned to slide along the elongated slot as the articulation rod moves the end effector relative to the shaft assembly. The articulation rod may be positioned to engage the fire lock to pivot the fire lock relative to the knife bar.

In embodiments, the surgical stapling apparatus may further include a pivot guide pivotally coupled to a proximal end portion of the end effector. The pivot guide may be positioned to cause the knife bar to bend around the pivot guide when the end effector is disposed in the articulated position. The pivot guide may be positioned to limit axial movement of the knife bar when the end effector is disposed in the unarticulated position.

Other aspects, features, and advantages will be apparent from the description, the drawings, and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with a general description of the disclosure given above, and the detailed description of the embodiment(s) given below, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a perspective view of a surgical stapling apparatus in accordance with the principles of the present disclosure, the surgical stapling apparatus including a loading unit with an end effector thereof shown in an unarticulated position;

FIG. 2 is a perspective view of the surgical stapling apparatus of FIG. 1 with the end effector thereof shown in an articulated position;

FIG. 3 is an enlarged, perspective view of a distal end portion of the surgical stapling apparatus of FIG. 1 with the end effector thereof shown in the articulated position;

FIG. 4 is an enlarged, perspective view of the loading unit of the surgical stapling apparatus of FIG. 1;

FIG. 5 is a perspective view of the loading unit of FIG. 4 shown with an outer tube thereof removed for clarity;

FIG. 6 is an enlarged, perspective view, with parts separated, of an inner shaft assembly of the loading unit of FIG. 4;

FIG. 7 is an enlarged, perspective view of the indicated area of detail delineated in FIG. 5;

FIG. 8 is an enlarged, perspective view, of a proximal end portion of the loading unit as shown in FIG. 5 with portions thereof shown in phantom for clarity;

FIG. 9 is an enlarged, cross-sectional, perspective view of the proximal end portion of the loading unit as illustrated in FIG. 5 and taken along section line 9-9 shown in FIG. 7;

FIG. 10 is an enlarged, perspective view of the indicated area of detail illustrated in FIG. 6;

FIG. 11 is a side, cross-sectional view of the loading unit as taken along section line 11-11 shown in FIG. 4, the loading unit illustrated in an unclamped position;

FIG. 12 is an enlarged, cross-sectional, side view of the indicated area of detail illustrated in FIG. 11;

FIG. 13 is a perspective view of the surgical stapling apparatus of FIG. 1 shown inserted through an access portal with the loading unit of the surgical stapling apparatus illustrated in a clamped position;

FIG. 14 is side, cross-sectional view of the loading unit as taken along section line 14-14 shown in FIG. 4, the loading unit shown in the clamped position;

FIG. 15 is an enlarged, cross-sectional, side view of the indicated area of detail illustrated in FIG. 14;

FIG. 16 is an enlarged, perspective view of the loading unit illustrated in FIG. 5 with the end effector thereof shown in the articulated position;

FIG. 17 is a top view of FIG. 16 with portions of the loading unit shown in phantom for clarity;

FIG. 18 is an enlarged, perspective view of the indicated area of detail illustrated in FIG. 16 with portions thereof shown in phantom for clarity;

FIG. 19 is side, cross-sectional view of FIG. 18 as taken along section line 19-19 shown in FIG. 18

FIG. 20 is an enlarged, perspective view of the distal end portion of the surgical stapling apparatus of FIG. 1 with the end effector thereof shown in the articulated position;

FIG. 21 is an enlarged, perspective view of the indicated area of detail illustrated in FIG. 20 with portions thereof removed for clarity;

FIG. 22 is a top, cross-sectional view of FIG. 21 as taken along section line 22-22; and

FIG. 23 is a top, cross-sectional view of FIG. 22 with the end effector shown in the unarticulated position.

DETAILED DESCRIPTION

Embodiments of the presently disclosed surgical stapling apparatus are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As commonly known, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Additionally, the term “proximal” refers to the portion of structure that is closer to the clinician and the term “distal” refers to the portion of structure that is farther from the clinician. In addition, directional terms such as front, rear, upper, lower, top, bottom, and the like are used simply for convenience of description and are not intended to limit the disclosure attached hereto.

In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

With reference to FIGS. 1-5, a surgical stapling apparatus 10 of the present disclosure includes a housing assembly 12 (which may include one or more handles that may be manually actuatable to fire surgical stapling apparatus 10), an adapter assembly 14 secured to housing assembly 12 and extending distally from housing assembly 12, and a loading unit 100 secured to adapter assembly 14 and extending distally from adapter assembly 14. Adapter assembly 14 and loading unit 100 define a longitudinal axis “X1-X1” that extends longitudinally therealong. Loading unit 100 may be disposable and/or include one or more disposable components.

Loading unit 100 of surgical stapling apparatus 10 is releasably secured to a distal end portion of adapter assembly 14 and includes a shaft assembly 140 and an end effector 110 pivotally coupled to shaft assembly 140 about a pivot axis “X2-X2” to enable end effector 110 to move (articulate) between unarticulated (see FIG. 1) and articulated positions (see FIGS. 2 and 3), as indicated by arrows “A.” In the articulated position, end effector 110 may be disposed at an angle relative to shaft assembly 140 (see FIG. 3). The angle may be any suitable angle, for example, in certain embodiments, the angle may be about 90 degrees, plus or minus 15 degrees. End effector 110 includes an anvil assembly 120 and a cartridge assembly 130 that houses a plurality of staples (not shown) in a reload or cartridge 130 a thereof that may be selectively replaceable. Cartridge 130 a of cartridge assembly 130 may be configured for selective replacement when end effector 110 is articulated to a predetermined angle, for instance, about 45 degrees. Cartridge assembly 130 is pivotally coupled to anvil assembly 120 about pivot axis “X3-X3,” as indicated by arrow “B,” between spaced (e.g., unclamped; see FIG. 1) and approximated (e.g., clamped; see FIG. 16) positions.

For a more detailed description of similar stapling apparatus, or components thereof, reference can be made, for example, to U.S. Pat. No. 8,070,033 to Milliman et al. (“the '033 patent”) and U.S. Patent Application Publication No. 2016/0242773 to Sadowski et al., the entire contents of each of which are incorporated herein by reference.

Turning now to FIGS. 4 and 5, shaft assembly 140 of loading unit 100 includes an outer tube 142 and an inner shaft assembly 150 that extends through outer tube 142. Inner shaft assembly 150 includes a proximal end portion 150 a that couples to a distal end portion of adapter assembly 14 (see FIG. 1) and a distal end portion 150 b that couples to a proximal end portion of end effector 110 of loading unit 100.

With reference to FIGS. 6-10, inner shaft assembly 150 of shaft assembly 140 includes a lower housing 152 and an upper housing 154 that support and I-beam assembly 156 and an articulation rod 158 therein. Lower housing 152 defines a guide channel 152 a centrally therethrough and a cutout 152 b in a proximal end portion thereof. Upper housing 154 defines a guide channel 154 a that is disposed in vertical registration with guide channel 152 a of lower housing 152 so that guide channels 152 a, 154 a are positioned to slidably receive I-beam assembly 156 therethrough. Upper housing 154 defines an insert recess 154 b and a lock recess 154 c that is vertically offset from insert recess 154 b and disposed at an angle relative thereto, for instance, a transverse angle. Upper housing 154 further defines an elongated channel 154 d disposed in a distal portion of insert recess 154 b. I-beam assembly 154 includes knife bars 156 a that support a lockout 156 b on a proximal portion thereof and an I-beam 156 c on a distal end portion of knife bars 156 a. Knife bars 156 a include a lip 156 d on a proximal end portion thereof. For a more detailed description of I-beam assembly 156, or components thereof, reference can be made to the '033 patent incorporated by reference above. Articulation rod 158 of inner shaft assembly 150 defines an elongated slot 158 a therethrough that is disposed in vertical registration with elongated channel 154 d of upper housing 154.

With continued reference to FIGS. 1-10, inner shaft assembly 150 of shaft assembly 140 supports a fire lock assembly 160 that is configured to prevent surgical stapling apparatus 10 from firing when end effector 110 is not in the articulated position, for example, about 90 degrees relative to shaft assembly 140 and/or longitudinal axis “X1-X1”. Fire lock assembly 160 includes a housing insert 162, a spring 164, and a fire lock 166. Housing insert 162 is configured to be received within insert recess 154 b and includes a base 162 a and a finger 162 b that extends distally from base 162 a. Spring 164 of fire lock assembly 160, which may be a compression spring, is receivable within cutout 152 b of lower housing 152 of inner shaft assembly 150 and is configured to engage fire lock 166 of fire lock assembly 160. Fire lock 166 includes a vertical arm 166 a and a lateral arm 166 b that extends in a laterally transverse direction from an upper portion of vertical arm 166 a. Fire lock 166 further includes a first branch 166 c that extends proximally from a lower portion of vertical arm 166 a and a second branch 166 d that extends proximally from lateral arm 166 b. First branch 166 c is configured to be received within cutout 152 b of inner shaft assembly 150 and spring 164 of fire lock assembly 160 to enable spring 164 to urge fire lock 166 distally. Vertical arm 166 a of fire lock 166 extends through elongated channel 154 d of upper housing 154 so that lateral arm 166 b of fire lock 166 extends across finger 162 b of housing insert 162 of fire lock assembly 160 and second branch 166 d of fire lock 166 seats in lock recess 154 c of inner shaft assembly 150.

In operation, as illustrated in FIGS. 11-23, I-beam assembly 156 of shaft assembly 140 is initially in a proximal position so that anvil and cartridge assemblies 120, 130 of end effector 110 are in the unclamped position (e.g., spaced or unapproximated) and fire lock assembly 160 is in a locked position. In the locked position, second branch 166 d of fire lock 166 is supported in lock recess 154 c of upper housing 154 and sloped at an angle so that lip 156 d of knife bars 156 a is coplanar with a proximal surface 166 e (FIG. 12) of second branch 166 d of fire lock 166. When anvil and cartridge assemblies 120, 130 are in the unclamped position, proximal surface 166 e of second branch 166 d is spaced a distance “d” from lip 156 d of knife bars 156 a to enable I-beam assembly 160 to distally translate the distance “d,” as indicated by arrows “C” (FIG. 14) for clamping anvil and cartridge assemblies 120, 130 together. As I-beam assembly 160 translates distally, I-beam 156 c of I-beam assembly 156 approximates anvil and cartridge assemblies 120, 130 into the clamped position (see FIGS. 13 and 14) of end effector 110, as indicated by arrows “B” (FIGS. 1 and 14). For a more detailed description of how I-beam 156 c approximates anvil and cartridge assemblies 120, 130, reference can be made to the '033 patent incorporated herein by reference. When end effector 110 is in the clamped position, lip 156 d of I-beam assembly 156 is engaged with proximal surface 166 e of second branch 166 d of fire lock 166 so that fire lock 166 prevents further distal advancement of I-beam assembly 156 (see FIG. 15) and firing of surgical stapling apparatus 10. In the clamped position, loading unit 100 can be advanced through a surgical access portal 200 (FIG. 13) for access to a surgical site within a patient. For a more detailed description of an example surgical access portal, reference can be made to U.S. Pat. No. 9,788,857 to Bettuchi et al., the entire contents of which are incorporated by reference herein. Once end effector 110 is advanced through surgical access portal 200, I-beam assembly 156 of shaft assembly 140 can be drawn proximally to unclamp end effector 110 for subsequent re-clamping of end effector 110 about tissue to be stapled by end effector 110.

To articulate end effector 110 of loading unit 100 to the articulated position (e.g., about 90 degrees), articulation rod 158 of inner shaft assembly 150 is drawn proximally (upon rotation of knob 14 a of adapter assembly 14; see FIG. 2), as indicated by arrow “D” (FIGS. 16-17). As articulation rod 158 translates proximally relative to fire lock 166 of fire lock assembly 160, vertical arm 166 a of fire lock 166 translates through elongated slot 158 a of articulation rod 158 so that an abutment edge 158 b (FIG. 18) disposed at a distal end portion of elongated slot 158 a of articulation rod 158 can engage a distal surface of vertical arm 166 a of fire lock 166. Continued proximal translation of articulation rod 158 causes fire lock 166 to compress spring 164 of fire lock assembly 160 and pivot to an unlocked position (FIG. 18), as indicated by arrows “E.” In the unlocked position of fire lock 166, end effector 110 is disposed in the articulated position and second branch 166 d of fire lock 166 is positioned above lip 156 d of I-beam assembly 156 so that lip 156 d of I-beam assembly 156 can translate beneath second branch 166 d of fire lock 166 for firing end effector 110 (FIG. 19) upon actuation of I-beam assembly 156.

As seen in FIGS. 20-23, loading unit 100 further includes a pivot guide 170 having a distal end portion 172 pivotally coupled to a proximal end portion of end effector 110 by a pin 180, and a proximal end portion 174 that is free and slidably received within outer tube 142 of shaft assembly 140. Pivot guide 170 further includes an arcuate inner surface 176 and a curved outer surface 178. When end effector 110 is in the articulated position (FIG. 22), curved outer surface 178 of pivot guide 170 is engaged with an inner surface of outer tube 142 so that outer tube 142 maintains arcuate inner surface 176 of pivot guide 170 in position to guide I-beam assembly 156 along a curved path “CP” into end effector 110. The curved path “CP” extends along arcuate inner surface 176 of pivot guide 170 and an arcuate inner surface 158 y of a distal portion of articulation rod 158. In particular, when end effector 110 is in the articulated position, arcuate inner surface 176 of pivot guide 170 and arcuate inner surface 158 y of articulation rod 158 define a predetermined radius “r”, for example, a perfect radius, to enable I-beam assembly 156 to curve smoothly into a knife channel 110 y of end effector 110 (e.g., without buckling) as knife bars 156 a of I-beam assembly 156 conform, for instance bend, to the predetermined radius “r” as I-beam assembly 156 is distally advanced for firing end effector 110.

With reference to FIG. 23, when end effector 110 is in the unarticulated position, outer tube 142 constrains a proximal portion of pivot guide 170 inwardly such that an inner edge 176 a of arcuate inner surface 176 and an inner edge 158 z of arcuate inner surface 158 y of articulation rod 158 apply opposing inward forces against outer surfaces of knife bars 156 a of I-beam assembly 156 to frictionally restrain axial movement of I-beam assembly 156.

Securement of any of the components of the presently disclosed devices may be effectuated using known securement techniques such welding, crimping, gluing, fastening, etc.

The various embodiments disclosed herein may also be configured to work with robotic surgical systems and what is commonly referred to as “Telesurgery.” Such systems employ various robotic elements to assist the clinician and allow remote operation (or partial remote operation) of surgical instrumentation. Various robotic arms, gears, cams, pulleys, electric and mechanical motors, etc. may be employed for this purpose and may be designed with a robotic surgical system to assist the clinician during the course of an operation or treatment. Such robotic systems may include remotely steerable systems, automatically flexible surgical systems, remotely flexible surgical systems, remotely articulating surgical systems, wireless surgical systems, modular or selectively configurable remotely operated surgical systems, etc.

The robotic surgical systems may be employed with one or more consoles that are next to the operating theater or located in a remote location. In this instance, one team of clinicians may prep the patient for surgery and configure the robotic surgical system with one or more of the instruments disclosed herein while another clinician (or group of clinicians) remotely controls the instruments via the robotic surgical system. As can be appreciated, a highly skilled clinician may perform multiple operations in multiple locations without leaving his/her remote console which can be both economically advantageous and a benefit to the patient or a series of patients. For a detailed description of exemplary medical work stations and/or components thereof, reference may be made to U.S. Patent Application Publication No. 2012/0116416, and PCT Application Publication No. WO2016/025132, the entire contents of each of which are incorporated by reference herein.

Persons skilled in the art will understand that the structures and methods specifically described herein and shown in the accompanying figures are non-limiting exemplary embodiments, and that the description, disclosure, and figures should be construed merely as exemplary of particular embodiments. It is to be understood, therefore, that the present disclosure is not limited to the precise embodiments described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure. Additionally, the elements and features shown or described in connection with certain embodiments may be combined with the elements and features of certain other embodiments without departing from the scope of the present disclosure, and that such modifications and variations are also included within the scope of the present disclosure. Accordingly, the subject matter of the present disclosure is not limited by what has been particularly shown and described. 

What is claimed:
 1. A loading unit for a surgical apparatus comprising: a shaft assembly; an end effector extending from the shaft assembly; an articulation rod positioned to articulate the end effector relative to the shaft assembly between an unarticulated position and an articulated position; a pivot guide that has a distal end portion pivotally coupled to a proximal end portion of the end effector and having an arcuate inner surface and a curved outer surface, the curved outer surface maintaining the pivot guide in position to guide the I-beam along a predetermined path when the end effector is in the articulated position; and a fire lock assembly movable in response to movement of the articulation rod, the fire lock assembly configured to selectively prevent the end effector from firing.
 2. The loading unit of claim 1, further comprising a beam assembly for firing the end effector.
 3. The loading unit of claim 2, wherein the beam assembly includes at least one knife bar, the knife bar supporting an I-beam configured to advance through the end effector.
 4. The loading unit of claim 3, wherein the fire lock assembly includes a fire lock that is positioned to engage the at least one knife bar to prevent the I-beam from firing the end effector.
 5. The loading unit of claim 4, wherein the fire lock assembly includes a spring that is positioned to urge the fire lock toward a first position to prevent the I-beam from advancing through the end effector.
 6. The loading unit of claim 5, wherein the articulation rod is positioned to move the fire lock to a second position as the end effector moves from the unarticulated position to the articulated position.
 7. The loading unit of claim 2, wherein the end effector includes an anvil assembly and a cartridge assembly that are pivotally coupled together and movable between an unclamped position and a clamped position.
 8. The loading unit of claim 7, wherein beam assembly is configured to position the anvil and cartridge assemblies in the clamped position as the beam assembly advances through the anvil and cartridge assemblies.
 9. The loading unit of claim 1, further comprising a pivot guide positioned to curve the beam assembly into the end effector.
 10. The loading unit of claim 1, wherein the fire lock assembly is positioned in the articulation rod.
 11. A surgical stapling apparatus comprising: a shaft assembly; an end effector extending from the shaft assembly; an articulation rod positioned to articulate the end effector relative to the shaft assembly between an unarticulated position and an articulated position; and a fire lock assembly received within the articulation rod and positioned to selectively prevent the end effector from firing.
 12. The surgical stapling apparatus of claim 11, wherein the end effector includes an anvil assembly and a cartridge assembly that are movable between an unclamped position and a clamped position.
 13. The surgical stapling apparatus of claim 12, further comprising a knife bar that is selectively movable through the end effector.
 14. The surgical stapling apparatus of claim 13, wherein the knife bar supports an I-beam on a distal end thereof, the I-beam positioned to advance into a proximal end portion of the end effector to move the anvil and cartridge assemblies from the unclamped position to the clamped position.
 15. The surgical stapling apparatus of claim 14, wherein the fire lock is selectively engageable with the knife bar.
 16. The surgical stapling apparatus of claim 15, wherein the fire lock prevents the I-beam from advancing distally beyond the proximal end portion of the end effector when the end effector is disposed in the unarticulated position.
 17. The surgical stapling apparatus of claim 15, wherein the articulation rod is positioned to engage the fire lock to pivot the fire lock relative to the knife bar.
 18. The surgical stapling apparatus of claim 11, wherein the fire lock is positioned to slide along the articulation rod as the articulation rod moves the end effector relative to the shaft assembly.
 19. The surgical stapling apparatus of claim 11, wherein the end effector is articulated approximately 90 degrees relative to a longitudinal axis defined through shaft assembly when in the articulated position.
 20. The surgical stapling apparatus of claim 13, further comprising a pivot guide pivotally coupled to the end effector, the pivot guide positioned to cause the knife bar to bend around the pivot guide when the end effector is disposed in the articulated position and positioned to limit axial movement of the knife bar when the end effector is disposed in the unarticulated position, wherein the pivot guide has a distal end portion pivotally coupled to a proximal end portion of the end effector by a pin, and wherein the pivot guide includes a proximal end portion that is free and slidably received within an outer tube of the shaft assembly. 